


A Ninja's Little Sister

by magicninja0925



Category: Teenage Mutant Ninja Turtles (Bay Movies), Teenage Mutant Ninja Turtles (TV 2012)
Language: English
Status: In-Progress
Published: 2020-07-02
Updated: 2020-07-02
Packaged: 2021-03-05 03:35:32
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 6
Words: 3,573
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25037854
Author URL: https://archiveofourown.org/users/magicninja0925/pseuds/magicninja0925
Summary: The turtles go about their everyday lives when they discover that Shredder has been experimenting with the DNA he managed to save from them. When they go to investigate, what they find isn't what they were expecting...
Kudos: 4





	1. The Shredder's Plan

Metal clashing against metal. Orders being shouted. Wounds inflicted. This is what battle is. And the turtles were in a heap of trouble. They were hopelessly outnumbered in Foot soldiers. The Shredder had obviously expected their coming here to investigate his experiments...

*3 hours earlier...*

The turtles were getting ready to go on patrol. They were just waiting on one person.

"Donnie!" Leo yelled for the hundredth time. "Let's go!"

Donnie came running out of his lab. "Okay okay I'm ready. Sheesh!"  
"Dude we've been waiting forever!" Mikey whined. 

Raph smacked the back of his head. "Don't be stupid. It's only been like 15 minutes."

"It felt like forever..." Mikey muttered, rubbing the back of his head. 

"Will you two stop?" Leo scolded. "Let's just go before there's not enough time to do anything."

They all stopped arguing and left the lair. They climbed out of the sewers and onto the rooftops.

"So Don, what were you doing in your lab for all that time anyway?" Raph asked. 

"I was going through the files I managed to hack from the Shredder," Donnie replied. "Turns out he's doing some weird experiments with the DNA he extracted from us."

"Dude, creepy," Mikey said. 

"How long has he been doing it?" Leo asked. 

"About 5 years since he had us contained," Donnie replied. 

"What's he been doing?" Raph questioned, looking at his purple clad brother. 

Donnie shrugged. "No idea." He checked one of his many gadgets. "But my indicators show that Shredder is nearby."

"How can you tell that?" Raph asked. 

"Excessive amount of metal."

"Makes sense," Mikey said with a grin.

"Let's go then," Raph said with a smirk. 

"For once, I agree with Raph," Leo said. "We can find out what the Shredder is up to."

The other two agreed and they went to where Donnie's tracker was saying. They easily got into the hideout. Unfortunately, the Shredder was waiting for them.

****Present****

"He was expecting us!" Raph shouted. 

"Thanks for pointing that out!" Leo yelled as he kicked a Foot soldier in the chest. 

"Raph! Mikey!" Donnie shouted to them. "Take this!"

He tossed a gadget to Mikey, who caught it and ran, Raph at his heels. 

"What're we supposed to do with this?" Raph asked. 

Mikey shrugged, turning the device over in his hands. "Hey there's a note!"

"Well what's it say?"

"'Find out what Shredder's up to. This will lead you to the lab,'" Mikey read. "Let's go to the lab then!"

Raph and Mikey followed the gadget's map to the lab.

"Mikey you look around," Raph said. "I'm gonna check the computers."

Mikey nodded and began searching the room. Raph went to the computers and began looking through the files. One in particular caught his eye. 

'Project 883: Genetics.'

He opened the file, and his eyes widened at what he found. 

'Genetic DNA:  
Leonardo: 20%.  
Michelangelo: 20%.  
Raphael: 20%.  
Donatello: 20%.  
Human DNA: 20%.  
Mutation successful.'

Raph quickly hit the print button and collected the paper as it came out of the printer. 

"Hey bro," Mikey said. "You might want to take a look at this."

Raph turned around and looked at his brother. In front of him was a containment tube, not unlike the ones his brothers had been held in 5 years ago. And inside this tube, was a little turtle. She looked about five and had shoulder-length red hair. She was slumped unconscious at the bottom of the tube.

"Mikey," Raph said. "Look at this paper."

Mikey took the paper from Raph. "What's it mean?"

"It means," Raph started. "This little turtle girl is our sister."


	2. Little Sis

"It means," Raph started. "This little turtle girl is our sister."

Mikey's mouth dropped. "What?"

"I'll have Don explain it to you later. Hit that button," Raph ordered. 

Mikey did as he was told and the tube opened. Raph leaned down and picked her up, carefully positioning her so she wouldn't get hurt. 

"Let's go get the others and get out of here," he told Mikey.

The two brothers left, taking the little turtle with them. 

"Leo!" Raph shouted as they reached the front room. "Don! We gotta go!"

Leo and Donnie kicked away a few more soldiers before using a smoke bomb and running towards the exit. Raph and Mikey followed, quickly jumping out and onto the rooftops. Leo and Donnie just noticed the turtle girl in Raph's arms when they stopped for a breath. 

"Who's that?" Leo asked. 

"She's our sister," Raph stated. 

"Our who now?" Donnie sounded very confused. 

"Mikey give him the paper," Raph ordered. 

Mikey handed Donnie the genetic paper Raph had printed out. Donnie read over the paper before his eyes widened. 

"She's our sister, Leo," Donnie concluded. "She has 20% of all of our DNA and 20% human DNA. That would explain the hair on a turtle."

Leo took the paper from Donnie. "Let me see that."

He looked it over and then looked at the sleeping girl Raph was holding. 

"Do you want me to take her Raph?" He asked. 

Raph shrugged. "If you wanna."

Leo nodded and Raph handed him the girl. She shifted but didn't wake. The turtles made sure they weren't being followed before jumping into an alleyway and into the sewers.

**Notes for the Chapter:**

> Sorry it's so short, but this was just kinda introducing the sister to the other two turtles. Read on, ninjas. :)


	3. Meeting Splinter

The four turtles quietly snuck back into the lair. They weren't worried about Splinter, they were worried about waking up their newfound sister. She was still asleep in Leo's arms. 

"Raph go get Splinter. Donnie go get your first aid kit and check her vital signs. And Mikey," Leo turned to his youngest brother. "Come up with a name for her."

Mikey quietly fist pumped. "Sweet!"

Donnie went into his lab and Raph into the dojo towards Splinter's room.

Leo laid the girl on the couch and she turned over in her sleep, reaching up to Leo as if wanting to be picked up. Leo gave a small smile and lifted her back off the couch, sitting down with her in his arms. Donnie came back in holding a small box. He took out a stethoscope and began checking the little turtle's vital signs. Raph came back out as well, Splinter right behind him. 

"Leonardo," he said. "Would you mind explaining?"

"Well," Leo started. "We were ambushed at Shredder's lair. We were going to investigate his experiments and he knew we were coming. So while Donnie and I held off the Foot, Mikey and Raph went to the lab and found her. Raph looked on the computer and... She's our sister, Sensei."

Before Splinter could ask how, Donnie handed him the paper while checking the girl's heartbeat. 

"Does she have a name?" Splinter asked. 

Leo shook his head. "Mikey's coming up with one."

Raph looked over at Mikey. "Hey! Mike! You gotta name for her yet?"

Mikey didn't respond for about a minute. He suddenly shot up from his seat on the ground. 

"Mackenzie!" He exclaimed. 

Donnie and Leo looked at him with a smile. Raph patted his brother's shoulder. 

"Good name, bro."

Mikey beamed. "Took me a whole 7 minutes to come up with that."

The little girl started to stir in Leo's arms. She shifted position so that instead of facing Leo's plastron, she was facing outwards, towards the rest of the family. She blinked open her bright green eyes and looked at the turtles and Splinter. 

Donnie looked her in the eyes. "Do you know who you are, little one?"

The little turtle shook her head. "All I remember was these guys in black suits putting this green stuff into my arm, and he also put in some clear stuff. I think he called it D-N-A?"  
The little girl tried to pronounce the acronym, obviously not knowing what it was or what it did. 

Donnie took the girl from Leo and sat her on his lap. "It is DNA. It's a genetic code. They put some of our DNA into your bloodstream, little one. Do you know what that means?"

She shook her head, confused. 

"It means you are our sister," Donnie explained. 

"Do you have a name, kid?" Raph asked. 

"I remember a few of the men calling me project 8 something. But I don't remember all the numbers," the girl replied. 

"Do you like the name Mackenzie?" Leo asked her. 

She tilted her head to the side, as if thinking. She then nodded. "Yeah."

"Mackenzie it is then," Raph said with a grin. 

Mackenzie was now a part of their crazy family.


	4. Nightmares

**Notes for the Chapter:**

> This is set a few days after they found her.

_Mackenzie was running. She was running through a long dark hallway. As she keeps running she sees a light at the end of the hallway and she calls out "Leo! Donnie! Guys are you there? Raph! Mikey!" She gets to end of the hallway and bursts into a large room. What she saw broke her. There, stood the Shredder. At the other end of the room lay three motionless figures, which Mackenzie recognized as Donnie, Leo, and Mikey. And at the Shredder's feet, lay Raphael. She screamed. A bloodcurdling scream that could have deafened anyone near her. ___

__Mackenzie shot up in bed, panting and crying. Instantly, her four newfound brothers were at her side. Leo lifted her off the bed, cradling her in his arms. Raph sat beside them, running his fingers through Mackenzie's red hair. Mikey laid one hand on her leg, rubbing it with his thumb comfortingly. And Donnie whispered soothing things to her. Within seconds, Mackenzie was calm again. She took a deep breath and blinked open her emerald green eyes._ _

__She looked into her brother's eyes; sky blue, forest green, sapphire blue, and coffee brown._ _

__"You okay, Mac?" Raph asked._ _

__When she didn't respond, they got worried._ _

__"Kenz," Leo pressed. "Are you alright?"_ _

__Mackenzie managed to shake her head, tears welling up in her eyes._ _

__"What happened, Kenzie?" Donnie asked._ _

__"You can tell us, little sis," Mikey reassured._ _

__Mackenzie took another deep breath and shakily told her brothers what happened. All of their expressions softened when they heard about her horrible nightmare._ _

__"What do you need Kenz?" Leo asked._ _

__Mackenzie didn't reply, she just crawled out of Leo's arms. She walked to the small closet in the hall and opened the door, looking for the biggest blanket they had. She found it, and pointed to it. Donnie, though confused, picked up the blanket. She led her four brothers into the living room._ _

__"Lay it out here," she said, pointing to the floor in front of the couch and TV. Donnie did as his sister asked and all four turtles watched her with confused expressions as she went into her room and grabbed her pillow and blanket. She set them in the middle of the blanket on the floor and faced her brothers._ _

__She looked up at them with pleading eyes, and Leo's expression went from confused to affection._ _

__"She doesn't want to sleep alone, guys," Leo told his brothers._ _

__The other three brothers thought for a moment before heading to their room and getting their own pillow and blanket. They set up their own spot, Donnie and Mikey on the outside, Leo and Raph on the inside on either side of Mackenzie. She cuddled closer to Raph, who opened one eye in surprise. He looked down at Mackenzie, who had now fallen asleep in his arms. He wrapped his other arm around his sister and fell asleep._ _


	5. Playing Games

Mackenzie rubbed her eyes. She sat up, seeing her four brothers asleep around her. The memories of last night flooded her mind. She shuddered at the thought. She stood, seeing a few action figures a few feet away. She walked over and picked them up before going back to her brothers.

**Leo ******

Mackenzie poked Leo until he woke up. He groggily opened his eyes.

"What's up, Kenz?"

She held up the action figures. "Play!"

Leo chuckled. "Alright."

He stood up, lifting Mackenzie into his arms. He brought her into his room, where he set her on the bed and grabbed a few other toys for her to play with. 

Mackenzie laughed and giggled as Leo played with her. He flew a rocket ship toy he had through the air.

"And it's off!"

Mackenzie giggled as she launched a toy missile at the rocket. Leo pretended to act surprised as the rocket ship fell out of his hand and onto the bed.

Mackenzie clapped. "Again! Again!"

Leo laughed. "Let's see if your brothers are awake."

As if on cue, as soon as Leo spoke, Raph walked into the room, obviously looking for Mackenzie.

"There you are," he said to her. She giggled and hid her face behind her hands.

"You wanna take her?" Leo asked. "I need to train and I just played with her for an hour."

Raph smiled. "Sure."

He walked into the room and lifted Mackenzie off the bed, holding her upside down. She laughed as she swung around.

**Raph ******

Raph carried Mackenzie into his room, where he laid her on the bed. She looked lost in thought for a moment. 

"Let's play hide and seek!" She squealed. 

Raph rolled his eyes, but he smiled. "Okay!"

While Raph covered his eyes and counted, Mac hid in the closet.

"...9...10!" Raph finished. "Here I come Mac!"

Raph looked around his room and under the bed. He knew she was in the closet, mostly because he heard her trying not to giggle. 

He walked to the closet and opened the door. "Gotcha!"

Mackenzie squealed and ran out of the closet, but Raph was faster. He grabbed her and started tickling her. She squealed and laughed. 

Raph stopped and looked up at a knock at his door. It was Donnie.

"Having fun?" He asked with a smile.

Mackenzie nodded, giggling.

"You wanna take her, Don?" Raph asked. "I'm gonna go train."

Donnie shrugged. "Sure. Come on, Kenzie."

Mackenzie jumped off the bed and took Donnie's outstretched hand.

**Donnie ******

Donnie led Mackenzie into his lab. He didn't really know what to do to entertain a 5 year old girl, so he gave her some of his old toys to play with before heading to his computer.

"Donnie," Mackenzie said, pulling on his arm. 

"Just a second," he replied. 

"Donnie!" Mackenzie whined.

Donnie sighed. "Okay okay. What is it, Kenzie?"

"Look!"

Donnie looked at what she was pointing at, and there on the floor, was a mini h2o model made out of Legos.

"Did you make that?" He asked, shocked.

Mackenzie nodded proudly. "Uh huh."

Donnie sat back in his chair. He knew Kenzie would have some trait of each of the brothers, since she had their DNA, but he didn't count on her getting his smarts.

"Wow," he breathed.

"What are you working on?" She asked, looking up at his computer screen.

He turned back to the computer. "I'm studying different blood samples to see if there's a way I could make a temporary human transformation serum."

Mackenzie was quiet for a second, as if thinking. "Cool!" She said finally, though it was clear she didn't understand what he said. "Can I help?"

Donnie widened his eyes for a moment, before he remembered that she had his brains. This stuff was probably interesting to her. She also had Raph's green eyes, Leo's skin tone, and Mikey's freckles.

"Yeah," he said, lifting her onto his lap so she could see the computer screen. "Sure."

They studied and compared the different blood types for about an hour and a half when Mikey walked into the lab.

"Hey, Don," he said.

"Hey," Donnie replied, not looking away from his computer.

"Mikey!" Mackenzie shouted, jumping off of Donnie's lap and running to Mikey.

"Can we play Mario Kart?" She asked.

"As long as you're done hanging out with Donnie, sure!" Mikey replied.

Donnie waved his hand. "Go ahead. I've had her for like 30 minutes over my time. It's your turn to watch her anyways."

Mikey shrugged. "Let's go little dudette!"

**Mikey ******

********

Mikey brought Mackenzie into the living room and plugged in the game system. He handed her a controller and turned on the game.

********

"Eat my dust!" She yelled as she passed him.

********

Mikey laughed. "Not so fast little miss!"

********

He passed her again.

********

This went on for three laps unit Mac finally won.

********

"Yes! I won! I won! I won!" She jumped up and did a little victory dance.

********

"No fair!" Mikey shouted. "I demand a rematch!"

********

Mac giggled and sat back down. "Okay! But I'm gonna win!"

********

"You're on!" Mikey countered.

********

They started another game and played for hours. In the end, Mac won.

********

"Yes!" She exclaimed.

********

"Okay okay," Mikey sighed. "You win."

********

The other three turtles came into the room.

********

"Bedtime, Mackenzie," Leo said.

********

Mac groaned. "Can I stay up a little longer?"

********

Raph shook his head. "You've been up all day."

********

She groaned again. "Fine."

********

Donnie led her to her room, where he helped her braid her hair. After that, her other three brothers came in and kissed her goodnight. They tucked her in and made sure she was asleep before leaving the room and going to bed themselves.

********

**Notes for the Chapter:**

> Yes, Donnie knows how to braid her hair XD


	6. Meeting April and Vern

**Third Person ******

********

"Mackenzie!" Leo called.

********

"Coming!" Mac called back.

********

"Leo are you sure this is a good idea?" Donnie asked.

********

"It's fine," Leo replied. "I already got permission from Splinter to take her up top. Plus, I think we should introduce her to April and Vern before they find out by accident."

********

Donnie nodded, satisfied that their sister would be safe.

********

Mac came into the living room. "Are we leaving already?" She asked in her squeaky five-year-old voice.

********

Mikey nodded. "Yes we are little dudette."

********

Raph knelt down to her level. "Ready?"

********

Mac nodded. "Okay."

********

Raph picked her up and she wrapped her arms around her big brother's neck. Raph then followed his brothers out of the lair.

********

******time skip brought to you by traveling through New York and me not knowing how to write that! XD******

********

Once the turtles arrived at the place where they were supposed to be meeting April and Vern, they sat on the rooftops, waiting. They saw a white van with the number 6 on the side pull in.

********

"They're here," Leo said.

********

April and Vern got out of the van as the turtles jumped onto the ground.

********

"Okay what was so important?" April asked.

********

"We wanted you to meet someone," Leo explained.

********

April glanced at Vern, who shrugged.

********

"Raph," Leo said.

********

Raph nodded and set Mac down.

********

"April, Vern, we'd like you to meet Mackenzie," Leo said, introducing her.

********

Mackenzie inched away from April and Vern, hiding behind Raph.

********

"It's okay," Raph whispered to her. "Go ahead." He gave her a small nudge towards Leo. She slowly made her way to her oldest brother and he took her hand.

********

"Say hi," Leo whispered.

********

Mac gave a shy wave. "Hi."

********

"Who's this, Leo?" April asked, smiling at the little girl.

********

"This is our little sister," Mikey replied.

********

Before she could ask any questions, Donnie handed her the genetic paper.

********

"This will explain everything," he said.

********

April looked over the paper before handing it to Vern.

********

Vern's eyes widened. "So now there's four walking talking turtles, and a little turtle."

********

Mackenzie glared at him. "I'm not that little!"

********

Raph chuckled a little. "She doesn't take well to insults."

********

"I wonder where she gets that, Raph," April said with a smile. 

********

"Very funny," Raph responded.

********

"She has physical traits of all of us," Donnie explained. "She has Leo's skin tone, Raph's eyes, Mikey's freckles, and I'm going to guess she'll have my height, since she's taller than she should be for a five year old. Then she's kinda picked up personality traits from all of us, being around us every day."

********

"What about personality?" Vern asked.

********

"She has Donnie's brains," Raph started. "Mikey's sense of humor, Leo's leader quality or whatever it is, and she has my attitude."

********

Mackenzie was still a little nervous around April and Vern, and Raph and April were the only two to notice.

********

"Kenz," Raph said. "Come here. April you too."

********

April and Mackenzie followed Raph a little ways away from the group.

********

"You don't have to be scared of them Mac," Raph said to Mackenzie.

********

She nodded. "I know."

********

"Go say hi to April," her older brother encouraged, nudging her towards the brunette.

********

Mac inched forward a little. April knelt down to her level.

********

"H-hi," Mac said shyly.

********

April gave a little smile. "Hi."

********

"You look different," Mackenzie pointed out.

********

April nodded. "I'm not the same as you. I'm human. You're a turtle, like your brothers."

********

Mackenzie tilted her head to the side. "I was mutated when I was a regular turtle. Mean men put mutagen and DNA into my bloodstream and turned me into this. They used Leo, Raph, Donnie, and Mikey's DNA. That's how I'm their sister."

********

April's eyes widened and she looked at Raph. He shrugged.

********

"Donnie's brains," was all he said.

********

April giggled.

********

"Raph! Mackenzie!" Leo called. "Let's go!"

********

Mackenzie pouted. "But I wanted to talk to the other guy too."

********

Leo chuckled. "You can talk to him some other time. It's getting late. Dad said you can start ninja training tomorrow."

********

Mac brightened. "Yay!"

********

Whenever the turtles referred to Splinter as anything other than 'dad' Mac would get confused.

********

Mac turned back to April. "Bye April."

********

"Bye," April replied.

********

Mackenzie walked over to Vern. "Bye bye."

********

Vern waved. Mac walked back over to Raph and he picked her up. Then, all five turtles disappeared into the night.

********


End file.
